A satellite telecommunication system comprises uplinks between gateway stations GS and an OBP processor (on board processor) mounted on board a satellite and downlinks between the OBP processor and user terminals. Generally, the uplink has a link budget, that is to say a signal-to-noise ratio, which is much better than the downlink. The OBP processor can be a transparent processor or a regenerative processor.
In the case where the OBP processor is transparent, the waveform used to transmit the data is modulated on the ground in the gateway station before being transmitted to the satellite. The processor on board the satellite receives and retransmits the waveform to the user terminals without processing it. However, in the very high throughput transmission systems, the use of a transparent processor is often unsuitable for transporting the necessary high throughput, because of a lack of frequency resources. To mitigate this problem, the current trend is to use wider frequency bands like the V and Q bands, but that causes the link budget to be degraded. In effect, the higher the frequency, the more severe the atmospheric attenuation phenomena. This necessitates the use of geographical diversity mechanisms, which leads to an increased complexity of the equipment used in the gateway station and greatly increases the cost of the transmission system.
In the case where the OBP processor is regenerative, the gateway station modulates the radiofrequency signals to be transported and converts them into a digital form before transmitting them over the uplink, to the satellite. The regenerative OBP processor therefore comprises equipment for demodulating the digital data received, a routing device, and equipment for re-modulating the data before transmitting them over the downlink, to the user terminals. The current regenerative processors are very complex because, because of the stack of the protocol layers used for the transmission of the data, it is necessary to perform, on board the satellite, a complete demodulation of the data received over the uplink, a switching and a routing of all the IP packets, then a complete re-modulation of the data to be transmitted over the downlink. Since the processing operations on board the satellite are performed on each IP packet, they are intensive and complex and require very significant on board computation power and processing power, which leads to electrical consumption and heat dissipation that are all the greater when the throughput of the data to be transmitted is high. The problem is that the processing capacity and the power available on board a satellite is limited and is not suited to very high throughputs.